1. Field of the Invention
The present invention relates to electrical switches in general, and, more particularly, to a safety switch for disconnecting a vehicle battery from the electrical system of the vehicle in the event of an accident.
2. Background Art
Motor vehicle accidents, whether involving an impact, such as to the front, rear, or side of the vehicle, or a rollover of the vehicle, frequently result in the release of flammable fuel. In the event that the vehicle is inverted by the accident, combustible engine oil may also pour out of the crankcase or sump and spill into the engine compartment. Not infrequently, such spilled fuel or oil ignites, with grievous results. Such ignition may be the result of any of a number of causes, however one common cause is the sparking of live wiring in the wrecked vehicle. Such sparking can take place not only in high voltage ignition systems, but may also take place elsewhere in the vehicle's wiring harness, which typically extends throughout the vehicle's body. Even if the engine, and thus its alternator, has ceased to operate, the vehicle's battery may continue to supply current to such circuits. The battery itself may also be tossed about or crushed in the engine compartment by the force of the accident, and its live terminal (typically the positive terminal) may come into contact with the metallic bodywork of the car, creating severe sparking, much like that of an arc welder. Such severe sparking is able to ignite not only flammable fuel, but also grease and spilled oil in the engine compartment. Because the hood is frequently crushed or otherwise unopenable as a result of the accident, it may be impossible to gain access to the engine compartment to suppress such a fire.
A number of devices have been proposed in the past to cut off current in the vehicle's electrical system in the event of an accident. U.S. Pat. No. 2,099,483, issued Nov. 16, 1937 to Hinde, discloses a circuit breaker which is wired into the electrical system between the ignition wiring and the ammeter. Two versions of this device are disclosed, one of which is a mercury switch: in the event that the vehicle overturns, the mercury runs along the inside of a cylindrical casing so as to ground the circuit and blow a fuse. In the second version of the device, the circuit is broken mechanically; when the device is in the vertical position, a conical closing member bridges an insulating annulus at the lower end of a conical bore so as to close the circuit, and when the device is tilted to the horizontal, the circuit closer slides in the bore so as to break the circuit. Both versions, however, fail to provide for circuit breaking action in the event of a vehicular impact other than a rollerover accident. Furthermore, they fail to eliminate the live wiring leading from the vehicle's battery up to the circuit breaker, or the live battery post itself, either of which may cause sparking in the event of an accident.
U.S. Pat. No. 2,145,543, issued Jan. 31, 1939 to Gross, discloses another switch which is wired in the ignition circuit between the battery and the ammeter. The device consists of a mercury-containing well having two terminals therein; so long as the mercury remains in the well, the circuit remains closed. A rod attached to the engine block extends adjacent to the reservoir. In the event of a frontal collision, the projecting rod breaks off the well, spilling the mercury and thereby cutting off the ignition. In the event that the vehicle is overturned, the mercury drains out of the top of the reservoir. The Gross device, however, also fails to eliminate either the live battery post or the live wiring running from the battery to the switch terminal. Furthermore, it is questionable whether the arrangement would be effective in the event of a rear or side impact.
U.S. Pat. No. 3,410,359, issued Nov. 12, 1968 to Mollison, discloses a device which includes a moving contact mounted on a conducting blade which normally biases the contact against a second contact, which in turn is connected to the battery. The other end of the blade is connected to the wiring harness. In the event of a collision, a spring loaded trigger is released against the blade so that the moving contact is pushed against another contact which is connected to ground, thereby disconnecting the battery from the wiring harness and grounding the harness. As with the previously described devices, the Mollison switch fails to eliminate all live wiring in a wrecked vehicle, inasmuch as both the exposed battery posts and the wiring leading from the battery to the circuit breaking device remain live even after the spring loaded trigger is released. Furthermore, Mollison does not appear to teach a device which will disconnect the electrical circuit in the event of a rollover accident, as opposed to a collision.
U.S. Pat. No. 3,830,331, issued Aug. 20, 1974 to Piazza, describes a device having a "z"-shaped male plug, one end of which is secured to the engine block, and the other end of which forms a prong which is slidably engaged by the sleeve of a female member. The sleeve of the female member extends from a lead cylinder, the opposite end of which is connected to a cable leading to the battery. When impact occurs, the inertia of the heavy lead weight on the female member causes it to move forward and disengage the sleeve from the prong of the male plug. Again, this device fails to completely eliminate the exposed battery posts and the possibility of live wiring in the wrecked vehicle; furthermore, the Piazza device would not appear to disconnect the electrical system in the event of a rollover accident, or a side or rear-end collision.
Accordingly, there exists a need for a device to effectively disconnect the wiring of a vehicle from the battery in the event of a front- or rear-end collision or a rollover accident so as to eliminate all possibility of live wiring in the vehicle, as well as for a device which will prevent live battery terminals or posts from coming into contact with the vehicle structure in such an accident and causing sparks which may ignite a fire.